Numerous lancing mechanism for obtaining blood samples have been developed. Many of these are optimized for effectiveness in quickly sticking a user with a lancing pin or blade to reduce the sensation of physical pain. Whether intentional or not, others are also designed in a manner that reduces physiological factors associated with obtaining a blood sample.
One such factor contributing to physiological discomfort in using known lancing mechanism results from loud slapping or popping noises certain devices make upon actuation. Another negative stimulus often noticed by users is recoil or sudden motion of the housing of a lancing device associated with lance firing. Anticipation of the noise or jolting motion of a lancing device can be as disconcerting as the needle stick itself. As observed by a Dr. Chapman, “Pain is far from being and emotionally neutral experience; it is almost always accompanied by emotional disturbance and distress. The physiologic accompaniments of such arousal vary with individual, but that may interact powerfully with the sensory mechanism of pain to exacerbate the pain state.” Chapman, The Management of Pain, 2nd Edition, Vol. 1, pg. 122 (1990).
Certain lancing devices are configured in such a way that they should run silently. Examples include those found in U.S. Pat. Nos. 4,924,879; 5,196,025; 5,304,193 and 5,938,679. These employ linkage or lever type mechanisms that advance and retract a lance without impulse loading or impact by or on the lance against opposing mechanism to cause serious noise. Other devices, even some employing camming or linkage mechanisms (such as in U.S. Pat. Nos. 5,527,334 and 5,554,166) do not.
As for the device described in U.S. Pat. No. 4,924,879 to O'Brien, it discloses a lancet driven and retracted into a cocked position by 180° oscillation of a torsion spring driven crank wheel attached to a connecting rod secured to a blade carrier constrained to slide in and out relative to an internal housing portion. A significant disadvantage of this system is presented by the fact that returning the mechanism to a cocked position results in the lance blade extension where it might present a danger in spite of an external housing provided to facilitate finger positioning. Cocking the mechanism is accomplished by a winding handle that winds a torsion spring one-half turn. A catch locks the loaded assembly until it is released by pressing a button. If cocked ahead of time, the system also presents the safety hazard of inadvertent misfire.
Similar hazards with respect to potential misfire due to stored energy in a cocked position are presented in the use of the devices described in U.S. Pat. Nos. 5,196,025 and 5,304,193. Each device utilizes a lever or linkage system that is flexed one way and then another to, respectively, fire and retract a lance member upon release from a cocked position by a latch.
The system described in U.S. Pat. No. 5,938,679 to Freeman, et al. includes an actuator having a crank wheel or link (referred to as a cam) and a connector link (referred to or pivotal arm) like the O'Brien device, but the wheel/link run in a full circle to actuate a blade assembly. The patent fails to disclose further structural details of the actuator. It does, however, describe a use where it moves an attached blade structure to penetrate and remain in a wound site for a preset length of time to fill a capillary tube associated with the blade and then retract. Such an actuator differs functionally from that of the present invention, which is intended to stick a patient and immediately retract to minimize pain. An actuator according to the present invention is not physically capable of such action or control.
It does, however, provide an exceptionally inexpensive, durable and easy to use means of actuating a lance. All this is accomplished in a smooth-operating, substantially noise free device, distinguishing the present invention over other know systems as well.